package main

import (
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"
	"unicode/utf8"
)

// testRedraw is the redraw interval the tests give a display, so that
// many redraws fit in a few milliseconds.
const testRedraw = time.Millisecond

// testDeadline bounds how long a test waits for a display to draw what
// it expects.
const testDeadline = 5 * time.Second

//nolint:paralleltest // replaces the process-wide os.Stderr
func TestStderrIsTTYFalseForNonTerminals(t *testing.T) {
	r, pipe, err := os.Pipe()
	if err != nil {
		t.Fatal(err)
	}

	regular, err := os.Create(filepath.Join(t.TempDir(), "stderr"))
	if err != nil {
		t.Fatal(err)
	}

	devNull, err := os.OpenFile(os.DevNull, os.O_WRONLY, 0)
	if err != nil {
		t.Fatal(err)
	}

	saved := os.Stderr

	t.Cleanup(func() {
		os.Stderr = saved

		for _, f := range []*os.File{r, pipe, regular, devNull} {
			_ = f.Close()
		}
	})

	cases := map[string]*os.File{
		"a pipe":         pipe,
		"a regular file": regular,
		os.DevNull:       devNull,
	}

	for name, f := range cases {
		os.Stderr = f

		if stderrIsTTY() {
			t.Errorf("stderrIsTTY() = true with stderr on %s", name)
		}
	}
}

func TestPhaseLabel(t *testing.T) {
	t.Parallel()

	phases := []string{"load", "walk", "hash"}
	if got := phaseLabel(phases, "walk"); got != "[2/3] walk" {
		t.Errorf("phaseLabel = %q, want %q", got, "[2/3] walk")
	}
}

// TestProgressLine checks the line a display shows in each state, ten
// seconds into the phase.
func TestProgressLine(t *testing.T) {
	t.Parallel()

	ago := time.Now().Add(-10 * time.Second)

	cases := []struct {
		p    *progress
		want string
	}{{
		p: &progress{
			label: scanPhase("load"), total: -1,
			waitingFor: "counting the records",
		},
		want: "[1/5] load: counting the records, elapsed 10s, eta unknown",
	}, {
		p:    &progress{label: scanPhase("hash"), total: 100, count: 20},
		want: "[3/5] hash: [20/100] 20%, 2 files/s, elapsed 10s, eta 40s",
	}, {
		p:    &progress{label: scanPhase("hash"), total: 100},
		want: "[3/5] hash: [0/100] 0%, 0 files/s, elapsed 10s, eta unknown",
	}, {
		p:    &progress{label: scanPhase("update"), total: 0},
		want: "[4/5] update: [0/0] 100%, 0 files/s, elapsed 10s, eta 0s",
	}, {
		p: &progress{
			label: scanPhase("walk"), total: 100, estimate: true, count: 20,
		},
		want: "[2/5] walk: [20/~100] 20%, 2 files/s, elapsed 10s, eta 40s",
	}, {
		// Past the estimate the walk cannot tell how long it has left.
		p: &progress{
			label: scanPhase("walk"), total: 100, estimate: true, count: 120,
		},
		want: "[2/5] walk: [120/~100] 120%, 12 files/s, elapsed 10s, " +
			"eta unknown",
	}, {
		// A first scan's walk has no estimate.
		p:    &progress{label: scanPhase("walk"), total: -1, count: 20},
		want: "[2/5] walk: 20 files, 2 files/s, elapsed 10s, eta unknown",
	}}

	for _, tc := range cases {
		tc.p.start, tc.p.rateStart = ago, ago

		if got := tc.p.line(); got != tc.want {
			t.Errorf("line = %q, want %q", got, tc.want)
		}
	}
}

// TestSetTotalStartsRate checks that setTotal starts a phase's rate,
// and so its ETA, from when the total becomes known, not from when the
// phase started waiting for it.
func TestSetTotalStartsRate(t *testing.T) {
	t.Parallel()

	waited := time.Now().Add(-20 * time.Second)
	p := &progress{
		label: scanPhase("load"), total: -1, start: waited, rateStart: waited,
	}

	p.setTotal(100)

	// Ten seconds after the total came, without waiting ten seconds,
	// 20 records are read.
	p.start = p.start.Add(-10 * time.Second)
	p.rateStart = p.rateStart.Add(-10 * time.Second)
	p.count = 20

	want := "[1/5] load: [20/100] 20%, 2 files/s, elapsed 30s, eta 40s"
	if got := p.line(); got != want {
		t.Errorf("line = %q, want %q", got, want)
	}
}

// awaitOutput waits until stderr holds want at least times times, and
// fails the test if it never does.
func awaitOutput(t *testing.T, stderr func() string, want string,
	times int,
) {
	t.Helper()

	deadline := time.Now().Add(testDeadline)
	for strings.Count(stderr(), want) < times {
		if time.Now().After(deadline) {
			t.Fatalf("stderr = %q, want %q at least %d times",
				stderr(), want, times)
		}

		time.Sleep(testRedraw)
	}
}

// TestPlainProgressPrintsAtStartAndEnd checks that when stderr is not a
// terminal a phase prints its line the moment it starts, before its
// first item, nothing for the items it completes before plainInterval
// has passed, and its line again as it ends.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestPlainProgressPrintsAtStartAndEnd(t *testing.T) {
	stderr := captureStderr(t)
	p := newProgress(progressParams{label: scanPhase("hash"), total: 1000})

	for range 1000 {
		p.increment()
	}

	p.finish()

	lines := strings.Split(strings.TrimSuffix(stderr(), "\n"), "\n")

	want := "[3/5] hash: [0/1000] 0%, 0 files/s, elapsed 0s, eta unknown"
	if len(lines) != 2 || lines[0] != want ||
		!strings.HasPrefix(lines[1], "[3/5] hash: [1000/1000] 100%, ") {
		t.Errorf("stderr lines = %q, want %q, then the line at 1000",
			lines, want)
	}
}

// TestPlainProgressPrintsWhileWaiting checks that a phase waiting with
// no completed items still prints a line every interval.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestPlainProgressPrintsWhileWaiting(t *testing.T) {
	stderr := captureStderr(t)
	p := startProgress(progressParams{
		label: scanPhase("load"), total: -1,
		waitingFor: "counting the records",
	}, false, testRedraw)

	awaitOutput(t, stderr,
		"[1/5] load: counting the records, elapsed 0s, eta unknown\n", 3)
	p.finish()
}

// lastFrame returns what a terminal shows of the frames a display drew:
// the last one. The library starts each frame with a carriage return
// and erases the previous one with spaces first.
func lastFrame(out string) string {
	var shown string

	for frame := range strings.SplitSeq(out, "\r") {
		if strings.TrimSpace(frame) != "" {
			shown = frame
		}
	}

	return shown
}

// TestTerminalRedrawsWhileWaiting checks that the terminal display of a
// phase keeps being drawn while the phase waits for its next item, and
// shows every item completed before the wait: a spinner's line with
// the elapsed time as of now, and the library's bar, which works out
// its elapsed time at each draw.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestTerminalRedrawsWhileWaiting(t *testing.T) {
	stderr := captureStderr(t)

	walk := startProgress(progressParams{label: scanPhase("walk"), total: -1},
		true, testRedraw)

	for range 50 {
		walk.increment()
	}

	// An hour into the phase, without waiting an hour.
	walk.mu.Lock()
	walk.start = walk.start.Add(-time.Hour)
	walk.mu.Unlock()

	awaitOutput(t, stderr, "elapsed 1h0m0s", 1)
	walk.finish()

	if shown := lastFrame(stderr()); !strings.Contains(shown, "50 files,") {
		t.Errorf("terminal shows %q, want a count of 50", shown)
	}

	hash := startProgress(progressParams{label: scanPhase("hash"), total: 100},
		true, testRedraw)

	for range 50 {
		hash.increment()
	}

	// Drawn with the 50 items, then twice more with none.
	awaitOutput(t, stderr, "(50/100,", 3)
	hash.finish()
}

// TestTerminalLinesFitWidth checks that every line a terminal display
// draws, bar or spinner, is narrower than the terminal at the size of a
// large scan. A line as wide as the terminal or wider would wrap, and
// every redraw would leave a line behind. stderr is not a terminal
// here, so the displays take it to be fallbackWidth wide.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestTerminalLinesFitWidth(t *testing.T) {
	stderr := captureStderr(t)

	cases := []progressParams{
		{label: scanPhase("content"), total: 9876543},
		{label: scanPhase("walk"), total: 9876543, estimate: true},
	}

	for _, params := range cases {
		p := startProgress(params, true, testRedraw)

		// 1234567 items two and a half hours into the phase, without
		// counting them one by one or waiting the hours.
		p.mu.Lock()
		p.count = 1234567
		p.start = p.start.Add(-150 * time.Minute)
		p.rateStart = p.start
		p.mu.Unlock()

		awaitOutput(t, stderr, "1234567", 1)
		p.finish()
	}

	lines := strings.FieldsFuncSeq(stderr(), func(r rune) bool {
		return r == '\r' || r == '\n'
	})

	for line := range lines {
		if n := utf8.RuneCountInString(line); n >= fallbackWidth {
			t.Errorf("a line of %d columns on a terminal %d wide: %q",
				n, fallbackWidth, line)
		}
	}
}

// TestProgressWarningsOnOwnLines drives the terminal displays, spinner
// and bar, through a run of warnings with no items between them, as when
// the walk meets many unreadable paths, for many redraws: every warning
// must land on a line of its own, never inside a redraw.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestProgressWarningsOnOwnLines(t *testing.T) {
	stderr := captureStderr(t)

	cases := []progressParams{
		{label: scanPhase("walk"), total: -1},
		{label: scanPhase("hash"), total: 10},
	}

	issued := 0

	for _, params := range cases {
		p := startProgress(params, true, testRedraw)

		// No pause between warnings: one written straight to stderr is
		// garbled only if a redraw lands while it is being written.
		for start := time.Now(); time.Since(start) < 50*testRedraw; issued++ {
			p.warnf("warning")
		}

		p.finish()
	}

	// A terminal shows each line as the text after its last carriage
	// return.
	shown := 0

	for line := range strings.SplitSeq(stderr(), "\n") {
		if !strings.Contains(line, "warning") {
			continue
		}

		shown++

		if text := line[strings.LastIndex(line, "\r")+1:]; text != "warning" {
			t.Errorf("terminal shows %q, want %q", text, "warning")
		}
	}

	if shown != issued {
		t.Errorf("%d warning lines, want %d", shown, issued)
	}
}

// TestTerminalStoppedShortKeepsCount checks that the terminal display
// of a phase that stops before its total, as an interrupted one does,
// is left showing the count it stopped at rather than a full bar.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestTerminalStoppedShortKeepsCount(t *testing.T) {
	stderr := captureStderr(t)
	p := startProgress(progressParams{label: scanPhase("hash"), total: 10},
		true, redrawInterval)

	p.increment()
	p.increment()
	p.finish()

	if shown := lastFrame(stderr()); !strings.Contains(shown, "(2/10,") {
		t.Errorf("terminal shows %q, want a count of 2 of 10", shown)
	}
}

// TestWarningAfterLastItemKeepsBar checks that a warning printed after
// a phase's last item, as for a failed read of the last file, leaves the
// phase's full bar on the terminal below the warning.
//
//nolint:paralleltest // captureStderr replaces the process-wide os.Stderr
func TestWarningAfterLastItemKeepsBar(t *testing.T) {
	stderr := captureStderr(t)
	p := startProgress(progressParams{label: scanPhase("hash"), total: 2},
		true, testRedraw)

	p.increment()
	p.increment()

	awaitOutput(t, stderr, "(2/2,", 1)
	p.warnf("warning")
	p.finish()

	if shown := lastFrame(stderr()); !strings.Contains(shown, "(2/2,") {
		t.Errorf("terminal shows %q, want a count of 2 of 2", shown)
	}
}